1. Field of the Invention
The present invention relates to an apparatus for balancing a rotating member and, more particularly, to an apparatus for balancing a rotating member by preventing eccentricity generated due to inequality in the material, and unbalance in the shape, of the rotating member when the rotating member is rotated at a velocity that is lower than a critical rotational velocity thereof.
2. Description of the Related Art
As widely known, a balancing apparatus is provided to remove eccentricity generated due to inequality in the material, and unbalance in the shape, of a rotary shaft when the rotary shaft is rotated. The balancing apparatus includes a groove and a plurality of balls inserted in the groove. The groove is formed in the thickness, along the circumference of a turntable. The balls are inserted in the groove together with an operational fluid. When the rotary shaft is rotated at a velocity higher than a critical rotational velocity thereof, the balls and the operational fluid are automatically located at a position such that eccentricity due to inequality in the material, and unbalance in the shape, of the rotating member can be compensated.
FIG. 1 is a top view of a conventional balancing apparatus. As shown in FIG. 1, a groove 50 having a predetermined width and a predetermined depth is formed in the thickness along the circumference of a turntable 30. A plurality of balls 5 formed of a same material in a same shape and a same size are disposed in the groove 50. The balls 5 have a predetermined rigidity and can be used semi-permanently.
When the turntable 30 is rotated, the balls 5 are accordingly rotated at the same time. When the rotational velocity of the turntable 30 becomes higher than a predetermined velocity, the balls 5 are continuously rotated rubbing each other.
However, since the balls 5 are formed of the same material, frictional heat may occur between the balls 5 due to the affinity between the balls 5 when they are rotated. The frictional heat makes the balls 5 adhere to each other resulting in a reduced lubricity.
It is therefore an object of the present invention to provide an apparatus for balancing a rotating member, which is operative to prevent reduction of lubricity between balls disposed in a groove and enhance the balancing efficiency by forming the balls with different materials or by forming them in different sizes.
According to an aspect of the present invention, a groove having a predetermined depth and a predetermined width is formed in the thickness along the circumference of a turntable having a center that is the same as a rotational center of a rotating member, and first balls formed of a first material and second balls formed of a second material that is different from the first material are alternately disposed in the groove.
Preferably, the first balls may be formed of a nonmagnetic material and the second balls may be formed of a magnetic material or vice versa. Alternatively, all the first and the second balls may be formed of a nonmagnetic material.
The nonmagnetic material may be a beryllium copper alloy or bronze, and the magnetic material may be formed steel or stainless steel.
In addition, selectively, the first balls may be surface-treated by MoS2, and the second balls may be surface-treated by diamond-like carbon, or vice versa.
Preferably, the sum of the number of first and second balls is an even number.
According to another aspect of the present invention, a groove having a predetermined depth and a predetermined width is formed in the thickness along the circumference of a turntable having a center that is the same as a rotational center of a rotating member, and first balls each having a first diameter and second balls each having a second diameter that is different from the first diameter are disposed. alternately in the groove.
Preferably, the shorter diameter of the first and the second diameters is in the range of from ⅓ to xc2xd of the longer diameter.